carb selection

**ultrafast30** · 03-11-2012

I have two sets of 70 hp carbs. Is there an advantage with the 75 stinger carbs over the 70 hp carbs. Am running on a 15' mid with nitro case . I have a set of 75 carbs buried in a box somewhere.

**Tim Kurcz** · 03-11-2012

Originally Posted by ultrafast30

I have two sets of 70 hp carbs. Is there an advantage with the 75 stinger carbs over the 70 hp carbs. Am running on a 15' mid with nitro case . I have a set of 75 carbs buried in a box somewhere.

What venturi size are these carbs? Also, two-jet or three jet?

Later model three-jets offer better tunability. 1.187" venturis are better for accel, 1.250" are better for top end.......... All need my velocity stacks to smooth transitions. $165 for a set of three includes shipping.

Tim

**David Mason** · 03-12-2012

Depends on your desired outcome. If you want better tunability, Tim is correct. If you are decent at dialing something in and leaving it be once you have it right, you should be fine. I have never used the venturi stacks personally. We won the NBRA Nationals last season, and also the high point championship in the SEH class (uses the 75 Stinger engines too). I know a few guys that use those rubbers on their carbs. Not sure where they got them, or who did the Mod's to their engines.....................

A cheaper alternative to the rubbers, is to modify your front cover spray shield. Once you cut the back out and bolt it back on, trust me, water can still get in there and drown it if you get hosed down.

**Tim Kurcz** · 03-12-2012

Originally Posted by David Mason

Depends on your desired outcome. If you want better tunability, Tim is correct. If you are decent at dialing something in and leaving it be once you have it right, you should be fine. I have never used the venturi stacks personally. We won the NBRA Nationals last season, and also the high point championship in the SEH class (uses the 75 Stinger engines too). I know a few guys that use those rubbers on their carbs. Not sure where they got them, or who did the Mod's to their engines.....................

A cheaper alternative to the rubbers, is to modify your front cover spray shield. Once you cut the back out and bolt it back on, trust me, water can still get in there and drown it if you get hosed down.

Actually, the $165 does not include the rubber turn down's. They attach with screw clamps to the CNC turned aluminum velocity stacks and are available from Home Depot or Lowes and need to be cut & sanded. Do it yourself for about $10 each, or $15 each if I secure them and do the work.

Tim

**ultrafast30** · 03-12-2012

both sets are 2 jet 1.187'. I have two 3 jet 1.25" carbs on a twin I built but I think I better run 3 carbs. I sure do like them for tuning.
I

**Tim Kurcz** · 03-14-2012

Originally Posted by ultrafast30

both sets are 2 jet 1.187'. I have two 3 jet 1.25" carbs on a twin I built but I think I better run 3 carbs. I sure do like them for tuning.
I

You're right, it's best to run three carbs on a triple. Others have tried a plenum with two, but it doesn't work as the fuel falls out of suspension when the throttle is opened too quickly. If you send the part number for your 1.25" carbs, I'll dig through inventory this weekend and find one for you. Or, might find a decent set of three.

Tim

**ultrafast30** · 03-17-2012

The only no I could get off the carbs was -EN432989. The tags are long gone. But they are definately three jet large bore.
Don

**ultrafast30** · 03-19-2012

Tim Any luck finding those carbs . I could use a whole set if you come across them. Probly work good with one of the exhausts you are workin on.
Don

**Tim Kurcz** · 03-19-2012

Hi Don,

Have been welding new towers and assembled two killer NBRA legal triples yesterday for a brand new big engine guy........ Will have time to look tomorrow night. There is only one remaining exhaust system available. It will be complete late April.

Tim